Current sensor and current sensor manufacturing method

• US 7,129,691 B2
• Filed: 11/01/2002
• Issued: 10/31/2006
• Est. Priority Date: 11/01/2001
• Status: Expired due to Term

• Current Assignee: Asahi Kasei EMD Corp (Asahi Kasei Corporation), Melexis Tessenderlo NV
• Original Assignee: Asahi Kasei EMD Corp (Asahi Kasei Corporation), Sentron AG (Sensinnovat BVBA)
• Inventors: Yamagata, Yo, Shibahara, Koji, Popovic, Radivoje, Racz, Robert
• Primary Examiner(s): Karlsen, Ernest
• Assistant Examiner(s): Vazquez, Arleen M.
• Application Number:
  US10/493,985
• Publication Number:
  US 20050030018A1
• Time in Patent Office: 1,460 Days
• Field of Search: 324/117.R, 324/117.H, 324/126, 324/127, 324/251
• US Class Current: 324/117.00H
• CPC Class Codes: G01R 15/20 using galvano-magnetic devices, e.g. Hall-effect devices , i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
• CPC Class Codes: G01R 15/202 using Hall-effect devices Hall elements in arrangements for measuring electrical power G01R21/08
• CPC Class Codes: G01R 15/207 Constructional details independent of the type of device used
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A low-cost, current sensor suitable for mass production and a manufacturing method thereof are provided. The current sensor is small with high sensitivity and can be packaged in a standard assembly line which is normally used when an integrated circuit is manufactured. Further, it is possible to obtain a sufficient shielding effect against a disturbance flux without degrading the detecting sensitivity of a flux. A first magnetic material 50 is bonded to the lower part of a current conductor 22C. The first magnetic material 50 has the function of converging and amplifying a flux 3 generated by the current to be measured. A second magnetic material 51 is bonded above a magnetic sensor chip 20. The second magnetic material 51 has a shielding function against a disturbance flux entering from the outside.

Claims

1. A current sensor comprising:

a housing of molded plastics;

a metallic current conductor through which a current to be measured flows;

a magnetic field sensor chip containing at least one magnetic field detection element, the magnetic field sensor chip being placed on a side of the current conductor;

a flux concentrator placed on the magnetic field sensor chip for urging a flux generated by the current flowing through the current conductor to pass through the at least one magnetic field detection element;

a plurality of input and output terminals, each of the input and output terminals having an end that is electrically connected to a corresponding terminal of the magnetic field sensor chip, wherein a portion of the current conductor carrying the magnetic field sensor chip lies in a first plane and said ends of the input and output terminals lie in a second plane oriented substantially parallel to the first plane, and wherein a distance between the first and second plane substantially disappears or is substantially the same as a thickness of the magnetic field sensor chip;

a first magnetic material located on a backside of the current conductor, said backside located opposite to the side that the magnetic field sensor chip is placed on; and

a second magnetic material located above the magnetic field sensor chip.

2. The current sensor as claimed in claim 1, wherein a position of the second magnetic material is set so as to satisfy 0.1α

≦

X≦

3.6α

where α

represents a whole length of the flux concentrator along a direction of the flux generated by the current flowing through the current conductor and X represents a distance between a magnetic detecting surface of the at least one magnetic field detection element and the second magnetic material.

3. The current sensor as claimed in claim 1, wherein the flux concentrator is composed of a pair of members having a gap of a predetermined width.

4. The current sensor as claimed in claim 2, wherein the flux concentrator is composed of a pair of members having a gap of a predetermined width.

5. A method of manufacturing a current sensor, comprising the steps of:

forming a thin plate-like metal into a leadframe containing a current conductor and input and output terminals;

placing a magnetic field sensor chip containing at least one magnetic field detection element on a side of the current conductor;

connecting electrical terminals of the magnetic field sensor chip to the input and output terminals;

forming a plastic housing by molding the current conductor, the magnetic field sensor chip and the input and output terminals;

separating the current conductor and the input and output terminals from each other;

providing a first magnetic material on a backside of the current conductor, said backside being located opposite to the side that the magnetic field sensor chip is placed on; and

providing a second magnetic material located above the magnetic field sensor chip.

6. The method according to claim 5, wherein a position of the second magnetic material is set so as to satisfy 0.1α

≦

X≦

3.6α

where α

represents a whole length of the flux concentrator along a direction of the flux generated by the current flowing through the current conductor and X represents a distance between a magnetic detecting surface of the magnetic field detection element and the second magnetic material.

7. The method according to claim 5, wherein the first and second magnetic material is provided before the plastic housing is formed.

8. The method according to claim 5, wherein the second magnetic material is provided after the plastic housing has been formed.